In a conventional technique, when plural images are to be jointed so as to obtain one image, areas that are overlapping or common to plural images are handled as “margins for pasting” (hereinafter, areas handled as “margins for pasting” are referred to as “common areas”) in order to join the images. Thereafter, relative positions between plural images are calculated in order to adjust the positions of the images on the basis of the calculated positions. When the plural images are jointed after the position adjustment, the common areas do not coincide with one another because such plural images involve, even in the common areas, movement of and changes in the object due to the difference in moments at which they were captured. Accordingly, unnatural ruptures can be made on the boundaries between common areas and the images.
In order to cope with this phenomenon, plural images are superposed, usually on a portion of the common areas near the boundaries so that those images are synthesized (referred to as synthesized areas, hereinafter), and thereby the boundaries do not become unnatural. Thus, an image obtained by joining images includes an area consisting of one image and an area consisting of a synthesized image, obtained by superposing plural images.
When plural images are superposed so as to be jointed as described above, a moving object included in the synthesized areas of those images is duplexed, which is problematic.
In order to solve the above problem, Patent Document 1 discloses an image synthesizing apparatus for generating an overlapped image by dividing, into plural areas, images to be overlapped, selecting one or plural images for each of the areas, generating a synthesized image for each area by using the area selected for each area, and repeating this process for all the areas so as to generate a synthesized image.
However, the image synthesizing apparatus in Patent Document 1 needs to divide an image into plural areas, and to perform processes in each of the areas, increasing the number of processes to be performed by the processor, which is a technical problem. Also, it is difficult for the image synthesizing apparatus to select an image for each area appropriately and automatically, which is another technical problem.
Also, the image synthesizing apparatus according to Patent Document 2 separates the objects and backgrounds from two images so as to obtain an image by synthesizing the background parts of the two images, and prompts a user to select one of the two objects separated from the two images so as to further synthesize the selected object and the image obtained by synthesizing the backgrounds.
However, the image synthesizing apparatus according to Patent Document 2 needs to divide the overlapped image into the object and the background, increasing the number of processes to be performed by the processor, which is a technical problem. Also, a user has to select an image for separating the object, which is another technical problem.
Patent Document 1
    Japanese Laid-open Patent Publication No. 2000-316125Patent Document 2    Japanese Laid-open Patent Publication No. 2004-72685